This application claims the priority of French Patent Application Serial No. 99/04844, filed Apr. 16, 1999, the subject matter of which are incorporated herein by reference.
The present invention relates, in general, to filling materials, and to a method of and arrangement for making such a filling material.
Filling materials of the type involved here, are generally made from a web-like sheet material of metal, in particular aluminum, or of dimensionally stable flexible material, especially plastic. The sheet material is typically perforated with evenly spaced slits in parallel relation to the longitudinal extension and stretched transversely across the sheet web. Filling material of this type is oftentimes used, i.a., for filling containers containing combustible fluid to prevent explosive combustion of liquids as a result of a rapid heat transfer.
It is known to provide the cuts in a flat sheet web in longitudinal direction of the sheet web, and then the sheet web is stretched in this flat form transversely to the longitudinal extension. As a result, only a slight deformation from the web plane is implemented. It has been shown that as a consequence of the slight deformation out of the web plane, the individual layers of the sheets bake together in the containers or interlock through movement, thereby creating free spaces within the container in which combustible liquid is present without the respective sheet inlays. As a consequence, explosive combustion may occur.
It would therefore be desirable and advantageous to provide an improved filling material to obviate prior art shortcomings, and to provide a method of and arrangement for making such a filling material.
The present invention provides for a filling material made from a web-like sheet which is perforated with evenly spaced slits, extending parallel in the direction of the longitudinal axis, and profiled transversely to the longitudinal axis.
The profiling of the sheet transversely to the longitudinal extension is maintained during stretching so that the deformation out of the sheet plane is effected in addition to the profiling during stretching, resulting, on the one hand, in a higher elevation out of the web area and, on the other hand, a more stable deformation transversely to the web area.
According to another feature of the present invention, the profile of the sheet may be formed by undulations extending preferably across the entire sheet width so as to realize a simple continuously producible profiling. An even greater strength of the sheet transversely to the sheet plane can be realized when providing the wavy profile with edged transitions.
According to another aspect of the present invention, a filling material of the above-stated type can be made by a method in which a web-like sheet of metal, in particular of aluminum, or of dimensionally stable flexible material, especially plastic, is provided with evenly spaced slits in parallel relation to one another and to the longitudinal extension of the sheet, subsequently formed with an undulated profile, and thereafter stretched transversely to the longitudinal direction, thereby realizing a filling material which has been profiled in a superior way.
According to still another aspect of the present invention, an arrangement for carrying out the above-stated method includes a conveyor for transporting the sheet, a cutting tool for formation of intermittent slits in the sheet, a device for stretching the slitted sheet, with the device having a clamping unit for the longitudinal edges of the sheet and an ascending contact body, and a profiling unit, positioned upstream of the stretching device, for providing the slitted sheet with an undulated profile. Such an arrangement is simple in structure and permits a continuous fabrication of such a filling material.
According to another feature of the present invention, the profiling unit is formed by a pair of interlocking profiling drums so that a profile is realized by rolling tools which permit a high processing speed. A reliable transport and also clamping of the edge of the sheet web in the clamping unit can be realized when the profile provided in the sheets by the profiling drums corresponds to the profile of the clamping unit for the longitudinal edges of the sheet. Hereby, the profile of the clamping unit may be provided at the margins of two clamping wheels which are embraced at their profiled peripheral surfaces over a portion of the circumference by respective clamping belts. The profiling unit thus also realizes a continuous uniform advance of the sheet. The same purpose and a high advance speed can be realized by arranging the center of both clamping wheels eccentric to the center of a rotating stretching body, whereby a maximum eccentricity is established in the area of the portion of the clamping wheels embraced by the clamping belt. In this manner, it is possible to omit lubrication of the material during its passage through the arrangement. This is especially relevant when the filling material is subject to further processing, e.g., by lacquer or other coats.
According to a variation, the clamping belt may be configured as a flat belt which bears upon the outer peripheral surfaces of radially outwardly directed projections of the clamping wheels profiled at their circumferential surfaces. This has the advantage that clamping of the sheet margins does not occur over the entire length but only along portions, so as to implement a stretching action in the area of the clamped regions entirely up to the margins, whereas those areas which are located between the clamped regions are subject to less stretching so that the sheet margin moves inwardly in an undulated manner. This is advantageous when introducing into the container bundles of stretched sheet material, bearing upon one another at their flat side regions, so that the bundles interlock and are hindered from shifting relative to one another as a consequence of the uneven surface.
According to another feature of the present invention, the clamping belt may be configured as profiled belt with a profile directed outwards and complementing the profile of the clamping wheels so that the sheet margins are held over their entire length in such a manner that as a consequence of the pre-profiling of the sheet web the profile engages like a gear in the outer profile of the clamping wheels and is held in this position by the toothed belt. In the area of maximum eccentricity, the spacing between the circumference of the stretching body and the clamping unit can hereby be greater than half the width of the stretched sheet material so that the sheet margins are pulled out between the clamping parts in the clamped region, thereby ensuring that the stretching of the sheet is effected up to the edge zone so that marginal regions do not remain unstretched as experienced in conventional constructions.
The rotating stretching body may be supported for free rotation, and thus solely moved by the sheet drawn above it so that relative speeds between the sheet and the stretching body are avoided and the sheet rolls off in the desired stretching over the rotating stretching body. In addition, the rotating stretching body may itself be supported eccentrically to thereby establish an even greater irregularity.
The filling material according to the present invention may be used not only for filling of containers for explosion-prone fluids but has shown to be very effective in solar collectors because a reflection of incident light quantity cannot occur when the filling sheets are blackened, but rather, incident solar energy is retained in the material as a consequence of inner reflections, resulting in a particularly good heating of water or air flowing through the solar collector.